Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee

Kawahito, Yousuke; Mizutani, Masami; Katayama, Seiji

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jwri37_02_019	pdf	1.34 MB	242	2012.09.22

論文情報

タイトル	Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee
著者	NRID 1000070379105 1000070379105 著者名 Kawahito, Yousuke
	著者名 Mizutani, Masami
	NRID 1000010144528 1000010144528 著者名 Katayama, Seiji
キーワード等	High-power fiber laser
	Laser-induced plume
	Stainless steel
	high-speed observation
	Spectroscopic analysis
	Laser probe measurements
抄録	The objective of this research is to obtain a fundamental knowledge of the optical interactions in a 10-kW fiber laser beam of 0.9-MW/㎟ power density and the plume or plasma induced during bead-on-plate welding of 20-mm-thick Type 304 stainless steel plate, on the basis of high-speed video observations, spectroscopic analysis and laser probe measurements. According to the high-speed observation results, the laser-induced plume was repeatedly generated from a keyhole at intervals of about 0.5-ms. The spectroscopy indicated that a bright plume emitted the line spectra of neutral atoms of alloying elements in Type 304 such as iron (Fe), chromium (Cr) and manganese (Mn). The temperature and the ionization degree of the laser-induced plume were calculated to be approximately 6,000 K and 0.02, respectively, by the Bolzman plots and via Saha’s equation. Furthermore, the probe laser passed horizontally through the plume was refracted at 0.6-mrad angle on average, which was much lower than the 90-mrad divergence of the focused fiber laser beam. The attenuation of the probe laser was measured to be about 4%, which was not mainly caused by Inverse Bremsstrahlung but by Rayleigh scattering. Subsequently, a stable laser welding process could be established at such an ultra-high power density that 11.5-mm-deep penetration was obtained even if the laser peak power was modulated 1-ms-periodically from 10 kW to 8.5 kW. It was consequently considered that the optical interaction between the 10-kW fiber laser beam and the weakly-ionized plume was too small to exert a reduction in weld penetration.
出版者	大阪大学接合科学研究所
	オオサカダイガクセツゴウカガクケンキュウジョ
	Joining and Welding Research Institute, Osaka University
収録物名	Transactions of JWRI
巻	37
号	2
開始ページ	19
終了ページ	25
刊行年月	2008-12
言語	英語
ハンドルURL	https://hdl.handle.net/11094/5073
ISSN	03874508
NCID	AA00867058
アクセス権	open access
出版タイプ	Version of Record
カテゴリ	紀要論文 Departmental Bulletin Paper
カテゴリ	Transactions of JWRI / Vol.37 No.2 (2008-12)

資源タイプ	紀要論文
ローカル資源タイプ	紀要論文
DCMI資源タイプ	text
DCTERMS.bibliographicCitation	Transactions of JWRI.37(2) p.19-p.25
DC.title	Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee
DC.creator	Kawahito, Yousuke
	Mizutani, Masami
	Katayama, Seiji
DC.publisher	大阪大学接合科学研究所
	オオサカダイガクセツゴウカガクケンキュウジョ
	Joining and Welding Research Institute, Osaka University
DC.language' scheme='DCTERMS.RFC1766	英語
DC.type' scheme='DCTERMS.DCMIType	text
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2008-12
DC.subject	High-power fiber laser
	Laser-induced plume
	Stainless steel
	high-speed observation
	Spectroscopic analysis
	Laser probe measurements
DCTERMS.abstract	The objective of this research is to obtain a fundamental knowledge of the optical interactions in a 10-kW fiber laser beam of 0.9-MW/㎟ power density and the plume or plasma induced during bead-on-plate welding of 20-mm-thick Type 304 stainless steel plate, on the basis of high-speed video observations, spectroscopic analysis and laser probe measurements. According to the high-speed observation results, the laser-induced plume was repeatedly generated from a keyhole at intervals of about 0.5-ms. The spectroscopy indicated that a bright plume emitted the line spectra of neutral atoms of alloying elements in Type 304 such as iron (Fe), chromium (Cr) and manganese (Mn). The temperature and the ionization degree of the laser-induced plume were calculated to be approximately 6,000 K and 0.02, respectively, by the Bolzman plots and via Saha’s equation. Furthermore, the probe laser passed horizontally through the plume was refracted at 0.6-mrad angle on average, which was much lower than the 90-mrad divergence of the focused fiber laser beam. The attenuation of the probe laser was measured to be about 4%, which was not mainly caused by Inverse Bremsstrahlung but by Rayleigh scattering. Subsequently, a stable laser welding process could be established at such an ultra-high power density that 11.5-mm-deep penetration was obtained even if the laser peak power was modulated 1-ms-periodically from 10 kW to 8.5 kW. It was consequently considered that the optical interaction between the 10-kW fiber laser beam and the weakly-ionized plume was too small to exert a reduction in weld penetration.
DC.format	application/pdf
citation_title	Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee
citation_author	Kawahito, Yousuke
	Mizutani, Masami
	Katayama, Seiji
citation_publisher	大阪大学接合科学研究所
	オオサカダイガクセツゴウカガクケンキュウジョ
	Joining and Welding Research Institute, Osaka University
citation_language	英語
citation_date	2008-12
citation_journal_title	Transactions of JWRI
citation_volume	37
citation_issue	2
citation_firstpage	19
citation_lastpage	25
citation_issn	03874508
citation_public_url	https://hdl.handle.net/11094/5073

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